Claude opus 5.5 shows significant reduction in punctuation usage

On September 26, @arena shared findings on X, revealing that Anthropic's Claude Opus 5.5 has significantly reduced its use of punctuation marks compared to its predecessor, Opus 5. The analysis, based on Text Arena high-reasoning responses from August and September 2026, showed improvements in 10 out of 12 writing metrics. Notably, Opus 5.5 uses approximately 0.8 dashes per 1,000 words, a 95% decrease from Opus 5's 15.2. Similarly, semicolon usage dropped from 6.10 to 1.64 per 1,000 words, a 73% reduction. The model also produced shorter sentences, averaging 10.03 words compared to Opus 5's 12.14. Despite shorter sentences, Opus 5.5 generated longer responses, averaging 481 words versus Opus 5's 453.